Jack pine (Pinus banksiana), also called scrub pine, Banksian
pine, or Hudson Bay pine, is a small-to medium-sized coniferous tree of
the northern forests of the United States and Canada, where it is an
important source of pulpwood, lumber, and round timber (1,10,15,16). It
grows farther north than any other American pine and is the most widely
distributed pine species in Canada. It is a pioneer species in succession
and invades areas where mineral soil has been exposed by major
disturbances such as fires. It usually grows in even-aged pure or mixed
stands on less fertile and drier soils than those required by other native
species in its range (38).

Habitat

Native Range

The major portion of the jack pine range is in Canada where its northern
boundary extends eastward from the Mackenzie River in the Northwest
Territories across the country to Cape Breton Island, NS. The range then
extends southwest through Maine, New Hampshire, northern New York, central
Quebec and northern Ontario, Michigan, extreme northwest Indiana,
northeast Illinois, then northwest through Wisconsin, Minnesota, Manitoba,
Saskatchewan, central Alberta, to extreme northeast British Columbia (72).

Within its range, jack pine is widely but not continuously distributed.
In Canada it is most abundant in Ontario, and in the United States, the
largest acreages are in Minnesota, Wisconsin, and Michigan (74). The only
significant artificial extensions of the jack pine range have been on
strip-mined areas in the central and northeastern States (61) and on the
sand hills of Nebraska (11).

- The native range of jack pine.

Climate

In the eastern part of its range, jack pine grows in a maritime climate
but elsewhere it is found in diverse continental climates characterized by
short, warm to cool summers, very cold winters, and low rainfall. The
average January and July temperatures range from -29° to -4° C
(-20° to 25° F) and from 13° to 22° C (55° to 72°
F), respectively. Average annual maximum temperatures range from 29°
to 38° C (85° to 100° F), and average annual minimum
temperatures are from -21° to -46° C (-5° to -50° F)
(61). Mean annual temperatures range between -5° and 4° C (23°
and 40° F) (74). The northern limits of the range closely parallel
the 29° C (85° F) mean annual maximum isotherm. Frost may occur
in some areas during any month and in the Northwest the range extends into
the permafrost zone. (61).

Average annual precipitation ranges from 250 to 1400 mm (10 to 55 in)
but 380 to 890 mm (15 to 35 in) are more usual. The average warm season
precipitation ranges from 150 to 640 mm (6 to 25 in). Annual snowfall is
from 76 to 508 cm (30 to 200 in), but over much of the range it is between
102 and 254 cm (40 to 100 in). Summer droughts are common in the
south-central and western portions of the range (61).

The average date of the last killing spring frost ranges from April 30
to about July 1; and the average date of the first killing fall frost
ranges from about August 10 to October 20. The frost-free period averages
from 50 to 173 days but is usually from 80 to 120 days. Generally,
temperature, rainfall, and frost-free period increase from the
northwestern toward the southeastern part of the range (61).

Soils and Topography

Jack pine is usually found on sandy soils of the Spodosol and Entisol
soil orders (81). It also grows on loamy soils, on thin soils over the
granites and metamorphosed rocks of the Canadian Shield, over limestones,
on peats, and on soil over permafrost (16,61,74).

Jack pine can grow on very dry sandy or gravelly soils where other
species can scarcely survive, but it grows best on well drained loamy
sands where the midsummer water table is from 1.2 to 1.8 m (4 to 6 ft)
below the surface. Jack pine does not grow naturally where the surface
soil is alkaline, but it does grow on soils overlying limestone. It can
grow on calcareous soils (pH 8.2) if a normal mycorrhizal association is
present. In southeastern New Brunswick, owing to a long fire history, jack
pine occupies vast areas of clayey soils and it is more common than red
pine on xeric sites that have high nutrient levels (61).

In well stocked stands in Minnesota and central Wisconsin, available
moisture-holding capacity in the upper 30 cm (12 in) ranges from 3 to 17
percent by weight. Site index improves with an increase in fine sand and
silt and clay in the upper soil layer, an increase in water-holding
capacity (up to a point after which it levels off), and an increase in
cation exchange capacity in the A and B horizons (61). Similar relations
between these soil factors and site index were found for plantations in
Wisconsin (82).

In a jack pine forest in northeastern Minnesota about 2580 to 3140 kg/ha
(2,300 to 2,800 lb/acre) ovendry weight of organic matter was returned to
the soil annually. The quantity of nutrient elements, expressed in
percentage of dry weight, in freshly fallen jack pine litter averages as
follows: calcium, 0.61; potassium, 0.16; phosphorus, 0.04; nitrogen, 0.58;
and ash, 4.15. The litter is acid with a pH of 3.8 to 4.3 (61).
Accumulated biomass of vegetation in jack pine stands more than 50 years
old in northeastern Minnesota was 89 000 kg/ha (79,400 lb/acre) on shallow
soils over bedrock, and 152 800 kg/ha (136,300 lb/acre) on deep till
soils. Biomass of the forest floor was 35 200 kg/ha (31,400 lb/acre) on
shallow soils and 50 300 kg/ha (44,870 lb/acre) on deep till soils.
Nutrients in the vegetation, forest floor, and soil were similarly higher
on the deep till soils (33). The above values largely agree with those
found on other sites for jack pine forest floor biomass, litter fall, and
nutrient transfer from jack pine forest to soil (28,49,78).

In the Lake States and Canada, jack pine grows most commonly on level to
gently rolling sand plains, usually of glacial outwash, fluvial, or
lacustrine origin. It occurs less commonly on eskers, sand dunes, rock
outcrops, and bald rock ridges. In the Lake States jack pine is found
chiefly at elevations between 300 and 460 m (1,000 and 1,500 ft), with a
maximum of about 610 m (2,000 ft) above sea level. In the East, jack pine
grows on a variety of sandy sites from near sea level up to about 610 m
(2,000 ft), with an outlier in New Hampshire at 760 m (2,500 ft) (61).

Associated Forest Cover

The Jack Pine forest cover type (Society of American Foresters Type 1)
(26) typically originates after forest fires. It is found in pure,
even-aged stands or as a majority of the stocking over vast areas of
Canada and to a much lesser extent in the Lake States and the northeastern
United States (61). In the boreal forest jack pine is also a component of
three other forest cover types-Black Spruce (Type 12), Paper Birch (Type
18), and Aspen (Type 16). In the northern forest region it is a component
of two forest cover types-Red Pine (Type 15) and Northern Pin Oak (Type
14). Outliers near southern fringes of the species' range are found in
various types of hardwood forest (12).

In Canada, six subtypes of jack pine may be recognized based upon the
edaphic and climatic conditions where they are found and on associated
species as follows: jack pine-balsam fir-black spruce (subtype a); jack
pine-feather moss (subtype b); jack pine-sheep laurel (subtype c); jack
pine-sphagnum. (subtype d); jack pine-labrador-tea (subtype e); jack
pine-lichen (subtype f) (26).

The preceding subtype descriptions apply primarily to eastern Canada.
However, jack pine forests in Saskatchewan bear close resemblance to some
of the subtypes described above (43).

Subtypes, as such, are not recognized in the Lake States. There are,
however, certain variants of the type, including jack pine-black spruce,
jack pine-red pine, and northern pin oak-jack pine (26).

Life History

Reproduction and Early Growth

Flowering and Fruiting- Jack pine is a monoecious species.
Ovulate cones are usually borne on primary and secondary branches in the
upper tree crown and staminate cones are usually borne on tertiary
branches lower in the crown. Ovulate cones are modified long shoots and
staminate cones are modified dwarf shoots (24).

In northeastern Wisconsin, bud initiation for the following year's shoot
systems begins in late June or early July. Staminate cone primordia are
initiated in early or mid-July but ovulate primordia are not initiated
until August. By early September the staminate cone primordia are about 1
mm (0.04 in) long and remain that size until spring. Then they elongate to
about 5 mm (0.2 in) by the middle of May and early June just before pollen
is shed. Rapid elongation up to several more millimeters occurs as the
pollen is shed. Time of pollen shedding (anthesis) varies greatly from
year to year depending on the weather (23).

Fertilization occurs about 13 months after pollination when the female
cone is approaching its maximum size (27). Jack pine is normally a
wind-pollinated, cross-fertilizing species but up to 25 percent or rarely
more natural selfing can occur (29,64). Under natural conditions, however,
survival of selfed and other inbred seedlings is severely reduced by
natural selection against the semilethal and other deleterious
characteristics carried by the inbred seedlings (67).

Cones mature and the seeds ripen late in the growing season of the year
after pollination. Various cone and seed characteristics, including cone
color, volume, fresh and dry weight, specific gravity, scale color, seed
color, and embryo length, can aid in determining seed ripeness. In
northeastern Wisconsin the best indicators of cone and seed ripeness are
cone color, 75 percent brown; insides of the cone scales, reddish brown;
seeds, dark brown or black; and cone moisture content, less than 45
percent of fresh weight. These indicators of cone and seed ripeness
coincide with the beginning of cone harvesting by squirrels about
September 10. Because specific gravity of the serotinous cones usually
remains above 1.0 at least until February, flotation techniques cannot be
used to evaluate cone and seed ripeness in jack pine (18).

Seed Production and Dissemination- Jack pine trees, particularly
under good early growing conditions, begin to flower at a younger age than
most other pine species (41,65,68). Under near optimum growing conditions
in the greenhouse and nursery, female flowering can be induced in a small
percentage of seedlings as early as 12 months from seed sowing (68). Male
flowering under these conditions usually does not begin until the fourth
year. An accumulated yield of 2,861,000 filled seeds per hectare
(1,158,000/acre) can be produced through the first 8 years in plantations
with 2.4 m (8 ft) between trees (67).

In naturally regenerated stands, jack pine typically begins to flower at
5 to 10 years under open-grown conditions but not until later in closed
stands (61). Once cone production in jack pine begins, it is fairly
regular and increases until crown competition becomes a factor. Seed
production differs from year to year but some seed is usually produced
every year and total crop failures are rare (31,61).

Seed yields per cone range from about 15 to 75 (72). Strongly curved
cones yield less seed than straight ones (72). Ovulate abortion on the
inner curvature of cones is twice that on the outer curvature (17). The
average number of scales per cone can be more than 80 but usually only a
little more than one-third of the scales, those in the upper end of the
cones, bear seeds (72).

Over much of its natural range jack pine bears predominantly serotinous
cones, but in the southern part cones are nonserotinous. Total seeds
stored on the trees in serotinous cones can reach more than 14.6 kg or 4
million seeds per hectare (13.0 lb or 1.6 million/acre) in well stocked
mature stands (61). As viability after 5 to 10 years may be significantly
reduced, however, only cones 6 years old or less should be collected (8).
Commercially cleaned seeds range between 156,500 and 551,000/kg (71,000
and 250,000/lb) with an average of 288,800/kg (131,000/lb) (45).

Well-stocked, mature stands in the Lake States dispersed an annual
average of 6,670 to 25,950 seeds per hectare (2,700 to 10,500/acre) over 5
years; much of the total crop remained in the unopened cones. In areas
with nonserotinous or partially serotinous cones, seed may be disseminated
during any season. The effective range of seed dissemination, as measured
by established seedlings, is about two tree heights although it is low
beyond one tree height (61).

The melting temperature of the resinous bonding material of the cone
scales is 50° C (122° F), but it is likely that the bonding
resin softens at lower temperatures in the nonserotinous types in the
southern portion of the species' range. The mechanism of cone opening in
both serotinous and nonserotinous cones is hygroscopic. Once the bonding
material of the cone scales is broken, the quantity of water in the scales
is the limiting factor in scale movement and flexing outward under drying
condition (35,61).

Jack pine cones open most readily during dry weather when the
temperature is at least 27° C (80° F), although many of them
remain closed until they are exposed to fire or high temperatures near the
ground after wind breakage or logging. Over most of its range where
serotinous cones are common, up to 50 percent may open on the sunny part
of the crown. Cones may also open in very cold winters when the
temperature is -46° C (-50° F) or colder (61).

Cone and seed crops in jack pine may be reduced by numerous agents (61).
Rainy weather at time of pollination may reduce seed set. Cone and seed
production are also reduced by cone and ovulate abortion (17,66), but the
severe losses previously attributed to abortion may be partially the
result of insect attacks. Within a cone, all the ovules near the base of
the cone abort and abortion decreases toward the tip (17).

Seedling Development- Germination is epigeal (45). Jack pine
seed usually germinates within 15 to 60 days under favorable conditions
(61), but some seeds require more than 100 days to germinate (72). Delayed
germination of direct seeding increased stocking between the first and
third year after sowing (60).

Under forest conditions with adequate moisture, seeds germinate when air
temperatures reach 18° C (64° F) but light also influences
germination (2,61). Under continuous light, germination was complete at a
range of temperatures from 16° to 27° C (60° to 80° F)
(2). Germination was markedly reduced at all temperatures when light was
excluded. The shade cast by slash and snags on burned-over or cut-over
areas to reduce surface temperature and drying undoubtedly contributes
substantially to the good germination often observed on such areas (16).

Type of seedbed is an important factor affecting jack pine seed
germination (16,61). In northeastern Minnesota, germination under clearcut
and partially cut jack pine stands averaged 60 percent on mineral soil, 49
percent on burned duff, 47 percent on scarified and shaded duff, and 17
percent on undisturbed duff (61). The poor germination on litter and humus
is caused by poor moisture conditions and it can be satisfactory in years
of above normal precipitation. Germination may be delayed by spring
drought (16). Associated species can affect germination, survival, and
growth of jack pine differentially, probably as a result of allelopathy
(13).

Survival on various seedbeds shows the same trend as germination (61).
Optimum conditions for jack pine seedling establishment and survival are
provided by mineral soil and burned seedbeds where competition from other
vegetation is not severe (16), the water table is high, and there is some
shade (61). Competition from shrubs and herbaceous vegetation, together
with smothering by fallen leaves, are important causes of seedling
mortality on sandy soils in Ontario. On clay soils in Manitoba and
Saskatchewan, competition from aspen and hazel are responsible for poor
survival. On similar soils in western Manitoba competing grasses kill many
seedlings (16).

Most of the older jack pine stands appear to have been established
following fires (61). Although jack pine seed usually germinates following
fire, most of the seedlings die unless the organic matter left on the soil
is less than 1.3 cm (0.5 in) thick. Most germination occurs the first and
second season following fire, with most mortality between the first and
second growing season. Unless conditions for germination and early
survival are favorable, good regeneration does not necessarily follow
burns (20,61).

Young seedlings grow tallest in full sunlight (48), although under
stands their initial abundance may be greatest in light intensities of 11
to 30 percent of full sunlight, but no seedlings are found at 60 percent
and higher crown cover (61).

Under forest conditions, seedling growth is slow in the first 3 years
but increases rapidly beginning in the fourth and fifth years. Seedlings
attain a height of about 5 cm (2 in) the first year, 15 cm (6 in) at 2
years, and 30 to 90 cm (12 to 36 in) at 4 years. Early growth of 2-0
seedlings in plantations is more rapid, amounting to 30 to 45 cm (12 to 18
in) per year on medium sites (61).

Shoot growth begins in late April and early May at Cloquet, MN, and
Chalk River, ON (62,63,80), and about May 10 in the Upper Peninsula of
Michigan (61). Essentially all height growth is completed in 61 to 68 days
at the three locations. Maximum growth rate approaches 1 cm (0.4 in) per
day in both Minnesota and Ontario. Although shoot growth in jack pine
ceases long before the end of the frost-free season, the remaining time
may be necessary to complete latewood growth, lignification, terminal bud
development, and hardening off to resist frost (80).

If favorable moisture conditions prevail in late summer, jack pine
frequently has a second period of shoot elongation and produces lammas and
proleptic shoots (62,63). Trees with lammas shoots had a longer growth
period than those without them but did not grow significantly less the
following year. The late growth does not result in detectable increases in
diameter growth and it may or may not result in false rings. Fall frost
injury resulting in frost rings, however, may be frequent in the current
shoots of trees with lammas growth.

Vegetative Reproduction- Under natural conditions jack pine does
not reproduce vegetatively. Jack pine cuttings from young trees can be
rooted but rooting ability decreases rapidly with increasing ortet age.
Cuttings from 4-month-old seedlings gave 75 percent rooting (7) but
average rooting was only 7 percent in cuttings from 6-year-old ortets and
5 percent in those from 10-year-old ortets (90). Clonal variation in
rooting percentage ranged from 0 to 31.

Aryl esters of indole auxins can enhance rooting of jack pine cuttings
taken from young seedlings. Phenyl indole-3-butyric (P-IBA) treatment
caused 12 percent more jack pine cuttings to root than did treatment with
indole-3-butyric acid (IBA), and up to 30 percent more than no treatment
(34).

Rooting needle fascicles has potential for establishing large clones in
a short time. Shearing the terminal buds on trees up to 5 years old
induces the fascicular buds to differentiate and develops shoots. Treating
such shoots from 2-year-old trees with IBA (0.1 percent) and placing them
in a heated rooting medium under a 20-hour photoperiod resulted in up to
70 percent rooting (71).

Jack pine can be grafted, most successfully using dormant scions and
when grafting is done just as the rootstock resumes growth in the spring.
Both early and delayed graft incompatibility may occur; the causes are
unknown (72). No complete jack pine plants have yet been propagated from
either callus tissue or cell suspension cultures (72).

Sapling and Pole Stages to Maturity

In well-stocked stands, jack pine develops into a short to medium-tall,
slender tree with a narrow, open crown covering 30 to 45 percent of the
stem (61). Crown ratios from 10 to 20 percent are not uncommon in dense
stands. Open-grown jack pine develops a stocky stem of poor form and a
wide, spreading crown with persistent branches, often to the ground.
Overstocked stands produce weak, spindly stems that are susceptible to
breakage by wind, ice, and snow (10).

Growth and Yield- During the first 20 years, jack pine in its
native range is the fastest growing conifer other than tamarack (61).
Seedlings reach 1.4 m (4.5 ft) tall in 5 to 8 years, depending on site. In
the Lake States, 20-year-old stands with 2,470 trees per hectare
(1,000/acre) on sites ranging from site index 12 to 21 m (40 to 70 ft)
average between 5.5 and 9.8 m (18 and 32 ft) tall, 6.7 and 20.0 m²
(29 and 87 ft²) in basal area, 5.8 and 10.2 cm (2.3 and 4.0 in) in
d.b.h. (46), and 14 600 and 62 800 kg/ha (13,000 and 56,000 lb/acre) in
ovendry weight of above-ground biomass (3).

The generalized equations used to derive these biomass estimates (3)
give results similar to biomass production reported in other natural jack
pine stands (22,32,37,51). Mean annual biomass production of 43-year-old
natural jack pine stands in Quebec ranged from 1.42 to 2.47 t/ha (0.63 to
1.10 tons/acre) (28); in 7- to 57-year-old jack pine in New Brunswick from
0.94 to 2.76 t/ha (0.42 to 1.23 tons/acre) (51); and in 20- to
100-year-old stands in Ontario from about 1.17 to 3.38 t/ha (0.52 to 1.51
tons/acre) (45). In 24- and 25-year-old plantations in the Lake States,
the highest mean annual biomass production was 58 percent higher than the
maximum reported in the literature, when seed source and site were
properly matched (89).

Annual height growth on medium sites (site index 17 m (55 ft)) in the
Lake States averages from 33 cm (13 in) at age 30 to 23 cm (9 in) at age
50. At age 80 years, annual height growth is only 13 cm (5 in) (46) On
typical sand plains sites, growth is about one site quality better where
the water table is 1.2 to 1.8 m (4 to 6 ft) from the soil surface than
where it is deeper (61).

Normally, mature trees are about 17 to 20 m (55 to 65 ft) tall and 20 to
25 cm (8 to 10 in) d.b.h., although some trees have attained 30 m (100 ft)
in height and 64 cm (25 in) in d.b.h. (46,61), and one tree listed by the
American Forestry Association in 1982 measured 73.4 cm (28.9 in) in d.b.h.
and 25.6 m (84 ft) tall. Stand basal areas seldom exceed 37 m²/ha
(160 ft²/acre) (46). Jack pine stands begin to disintegrate after 80
years on the best sites and after 60 years on the poorest sites. Vigorous
trees 185 years old have been found in northwestern Minnesota, however.
The oldest tree reported- 230 years old- was found east of Lake Nipigon in
Ontario (61).

Growth is somewhat slower, but maintained longer, in Canada. Average
stocking on sites having a site index range of 14 to 17 m (45 to 55 ft) in
southern Manitoba produces a culmination of mean annual increment at 50 to
60 years with 1.6 to 3.2 m³/ha (23 to 46 ft³/acre) of
merchantable material (9). For average site (site index 14 m (45 ft)) and
stocking in Saskatchewan, mean annual increment culminates at about 70
years with 2.0 merchantable m³/ha (28 ft³/acre) (42). In fully
stocked stands on average sites (site class 2) in Ontario, mean annual
increment culminates at about age 60 with 2.7 m³/ha (38 ft³/acre)
of merchantable material (54).

Yields from well-stocked, unmanaged jack pine stands in the Lake States
at 60 years are shown in table 1 (46), along with yields from well-stocked
unmanaged stands in Saskatchewan (42). Rotation age of 40 to 50 years is
recommended to produce pulpwood and 60 to 70 years is recommended to
produce poles and sawtimber.

Table 1- Yields of unmanaged jack pine stands in the
Lakes States and in Saskatchewan by age and site index

Age

Height¹

Basalarea

Totalvolume

Merchantable volume

yr

m

m²/ha

m³/ha

m³/ha

Lakes States

Site index² 12.2 m

30

8.2

12.2

41

31

40

10.4

15.8

67

52

50

12.2

18.4

92

71

60

13.7

20.4

114

88

Site index 18.3 m

30

12.2

23.0

115

89

40

15.5

27.3

174

134

50

18.3

30.1

224

173

60

20.4

31.7

265

206

Saskatchewan

Site index 10.1 m

30

5.8

11.7

45

10

40

8.2

14.0

66

34

50

10.1

15.8

85

56

60

11.9

17.0

102

75

Site index 17.4 m

30

11.6

19.3

112

61

40

14.6

23.2

140

98

50

17.4

26.2

168

134

60

19.8

28.2

195

165

ft

ft²/acre

ft³/acre

ft³/acre

Lakes States

Site index 40 ft

30

27

53

580

448

40

34

69

956

736

50

40

80

1,311

1,008

60

45

89

1,631

1,264

Site index 60 ft

30

40

100

1,647

1,272

40

51

119

2,484

1,920

50

60

131

3,194

2,472

60

67

138

3,789

2,936

Saskatchewan

Site index 33 ft

30

19

51

645

150

40

27

61

940

485

50

33

69

1,210

800

60

39

74

1,460

1,070

Site index 57 ft

30

38

84

1,600

865

40

48

101

2,000

1,403

50

57

114

2,405

1,910

60

65

123

2,785

2,360

¹Mean
height of dominants and codominants.
²Height of dominants and codominants at 50 years.

Rooting Habit- Jack pine frequently develops a taproot as a
seedling and maintains it to maturity. During the first growing season
under natural conditions the seedling root system penetrates to a depth of
13 to 25 cm (5 to 10 in). By the end of the second growing season jack
pine seedlings on typical sandy soils in the open have a dry weight
between 1 and 2 g (0.04 and 0.08 oz), have developed 8 to 10 cm (3 to 4
in) tops, and have root systems from 28 to 33 cm (11 to 13 in) deep and
from 46 to 61 cm (18 to 24 in) wide. On a moist sandy soil with the water
table about 76 cm (30 in) below the surface in Upper Michigan, roots
penetrated to 53 cm (21 in) in 2 years but only to 61 cm (24 in) by 7
years; the lateral spread, however, increased from 0.9 to 1.2 m (3 to 4
ft) at 2 years to 4.3 to 4.9 m (14.0 to 16.2 ft) at 7 years. In the
7-year-old trees the average volume of the top, stem, branches, and
foliage was about 4000 cm³ (244 in³) as compared to 1200 cm³
(73 in³) for the root system (61).

In northern Minnesota, root growth begins when the temperature reaches 4°
C (40° F) in the upper 15 cm (6 in) of soil, usually within a week of
the onset of shoot growth. Root growth ceases in the fall when soil
temperature drops to 7° C (45° F) for 6 days or more. In some
years root growth may begin in April and continue to late October.
Seven-year-old trees elongated their lateral roots an average of 38 cm (15
in) in 1 year (61). In Manitoba, root development of jack pine growing on
dry and fresh sands was confined mainly to the taproot for the first 1 to
3 years, but lateral branching became increasingly common on 3- to
4-year-old seedlings. Mycorrhizae were found on 1-year-old seedlings (16).

On deep, well-drained soils the roots may penetrate below 2.7 m (9 ft).
Trees without distinct taproots usually have lateral roots that turn and
grow downward as they approach other trees. The bulk of the root system,
however, consists of laterals confined largely to the upper 46 cm (18 in)
of soil; much of the root system is in the upper 15 cm (6 in) of soil. In
25-year-old jack pine stands in central Wisconsin, the dry weight of all
roots in the upper 1.5 m (5 ft) of soil was 10 980 to 13 790 kg/ha (9,800
to 12,300 lb/acre) (61). A 40-year-old stand of jack pine in northern
Minnesota produced 28 000 kg/ha (24,978 lb/acre), ovendry weight, of roots
greater than 0.5 cm (0.2 in) and stumps less than 15 cm (6 in) tall (73).

Reaction to Competition- Jack pine is one of the most
shade-intolerant trees in its native range. It is the least tolerant of
its associated pine species and is slightly more tolerant than aspen,
birch, and tamarack. Jack pine may be more tolerant in the seedling stage
and often requires some shade on dry sites to reduce surface temperatures
and evapotranspiration. Soon after seedlings are established, however,
they should receive full sunlight to assure survival (10,61). Overall,
jack pine can most accurately be classed as intolerant of shade.

Overstocked jack pine seedling and sapling stands with 4,950 or more
trees per hectare (2,000/acre) should be weeded or cleaned (precommercial
thinning) to improve growth and development. Otherwise such stands may
stagnate because natural thinning in jack pine stands is slow except on
the best sites (10). A study in northern Minnesota, wherein direct seeding
produced a stand averaging 32,100 trees per hectare (13,000/acre) at age 5
years, compared the growth of no thinning with thinning to square spacings
of 1.2, 1.8, and 2.4 m (4, 6, and 8 ft). Twenty-two years later the
treatments averaged 9, 10, 13, and 15 cm (3.7, 4.1, 5.1, and 5.8 in) in
d.b.h., respectively (14). Planting, direct seedings, and precommercial
thinnings should have a goal of 2,000 to 3,000 trees per hectare (800 to
1,200/acre) by age 10 years (19,30).

Jack pine is a pioneer species on burns or other exposed sites. In the
absence of fire or other catastrophes, jack pine is succeeded by more
tolerant species, but on the poorest, driest sites it may persist and form
an edaphic climax. In loamy sands and sandy loams in northern Minnesota,
the usual succession is from jack pine to red pine to eastern white pine
to a hardwood type composed of sugar maple (Acer saccharum), basswood
(Tilia americana), and northern red oak. Frequently, the red pine
and white pine stages are absent and jack pine is followed by speckled
alder (Alnus rugosa), American hazel (Corylus americana), beaked
hazel (C. cornuta), paper birch, and quaking aspen. This stage is
followed by either the sugar maple-basswood association or spruce-fir. On
loamy soils in northeastern Minnesota and parts of Canada, jack pine is
succeeded by black spruce, white spruce, balsam fir, and paper birch.
Eventually, the paper birch is eliminated from this association. In parts
of northwestern Canada, jack pine may be replaced directly by white
spruce; in parts of eastern Canada, the immediate succession may be to
pure black spruce (10,26,61).

Damaging Agents- Jack pine is subject to many agents that cause
damage or mortality. Young jack pines are especially susceptible to early
spring fires. Severe drought may kill many seedlings, particularly on
coarse soils. All young jack pines less than 1.5 m (5 ft) tall and 55
percent of those from 1.5 to 3.7 m (5 to 12 ft) tall were killed by 123
days of flooding in northern Minnesota. Heavy populations of white-tailed
deer can kill young jack pines up to 2.1 m (7 ft) tall, retard total
height growth to half its potential, and deform most trees so they have
little future value for timber products. Snowshoe hares can severely
damage jack pine reproduction, particularly in dense stands in trees less
than 4 cm (1.5 in) in d.b.h. (16,61). Jack pine seedlings are greatly
damaged by elk in western Manitoba when animal populations are high, and
meadow voles cause occasional damage and mortality by gnawing the bark off
main stems and lower branches (16). Porcupines can cause extensive damage
in older stands (74).

Several sawflies attack jack pine. Trees are often killed because the
sawflies feed on both old and new needles. The pine tussock moth (Parorgyia
plagiata) commonly defoliates large areas of sapling- and pole-size
jack pine. The jack pine budworm is the most important defoliator of jack
pine in the northeastern United States (61,84).

Several diseases commonly attack young jack pines and reduce survival
and growth. A needle rust fungus (Coleosporium asterum) causes
some defoliation of seedlings. Diplodia blight (Diplodia pinea) frequently
results in a shoot blight of jack pine seedlings under nursery conditions.
Sirococcus shoot blight (Sirococcus strobilinus) has also caused
seedling losses in Lake States nurseries. Scleroderris canker (Gremmeniella
abietina) causes serious losses in both nursery stock and young
plantations. Before nursery control programs for this disease were
instituted in the Lake States, this fungus killed an average of 40 percent
of seedlings in plantations established with infected stock (77).

Jack pine is susceptible to a number of rust fungi that cause both
growth loss and tree mortality. Many of these rusts are disseminated by
infected nursery stock. The sweetfern blister rust (Cronartium
comptoniae) sometimes kills many young seedlings and reduces the
growth of survivors. More prevalent is the pine-oak (eastern) gall rust
(Cronartium quercuum), which may infect up to 50 percent of young
seedlings, killing many of the seedlings with galls on the main stem.
Young jack pine in Minnesota have been severely cankered by stalactiform
rust (Cronartium coleosporioides). In recent years the
pine-to-pine (western) gall rust (Endocronartium harknessii) has
been found throughout the Lake States in young jack pine stands. The
importance of this rust is its potentially rapid rate of spread. This rust
can infect directly from pine to pine without spending parts of its life
cycle on an alternate host as do all the previously mentioned rusts (77).

Sapling- and pole-size jack pine frequently show severe needlecast (Davisomycella
ampla). This fungus often causes loss of all but the current year's
needles. Although affected trees suffer growth loss, the disease seldom
causes mortality. Diplodia blight frequently kills branches and often the
entire tree. This disease appears to be stress related and may reach
epidemic status following drought. The European strain of scleroderris
canker is currently killing many jack pine in northern New York and will
cause serious losses if it reaches the major range of jack pine (77).

The rust fungi mentioned under seedling disease also cause extensive
mortality in pole-size stands. The pine-oak (eastern) gall rust has caused
severe losses in jack pine stands in northern Wisconsin. In some pole-size
stands the disease is so prevalent that the stands have become worthless
and have been destroyed (77).

Windthrow is not a serious problem in jack pine stands except on shallow
soils or when more than one-third of the stand basal area is removed in
thinnings. Stem breakage from wind, ice, and snow is more common (10).

Cone and seed production can be decreased by numerous factors. Red
squirrels and other rodents destroy cones and consume seeds (18,61,69,72).
Low-vigor trees may produce much pollen but little seed. Pine-oak
(eastern) gall rust damages trees resulting in smaller and aborted ovulate
cones. Birds may be important consumers of jack pine seeds that fall to
the ground or are directly sown (61). Cone and seed insects may cause
serious losses. In one study in northeastern Wisconsin, numerous insect
species were found attacking conelets and cones (57). The jack pine
budworm (Choristoneura pinus pinus) destroyed 12 percent of the
conelets. A mirid (Platylygus luridus) was observed piercing
conelets as well as shoots and needles and was apparently responsible for
a severe but unknown conelet abortion rate. The most prevalent insect
attacking cones was the cone borer (Eucosma monitorana) which
killed 10 percent of the cones. Other insects responsible for a total of
about 4 percent cone mortality were the webbing coneworm (Dioryctria
disclusa), red pine cone beetle (Conophthorus resinosae), jack
pine budworm, and cone midges (Lestodiplosis graddator, Resseliella
silvana, and Asynapta hopkinsi) (57).

Special Uses

The most notable special use for jack pine is as a breeding area for the
Kirtland's warbler, a rare and endangered species. The Kirtland's warbler
requires homogeneous stands of jack pine between 1.5 and 6 m (5 to 20 ft)
tall (about 7 to 20 years old); stands are preferably larger than 32 ha
(80 acres) (52).

Jack pine stands can be an important part of the visual resource for
recreation areas; they stabilize watersheds, produce areas for blueberry
picking, and provide food and shelter for wild game species, including the
snowshoe hare and the white-tailed deer (10).

Genetics

The various environments in which jack pine grows over its wide range
have provided ample opportunity for differentiation and natural selection
(72).

Virtually the entire present range of jack pine was glaciated during the
most recent Wisconsin stage that reached its maximum about 18,000 years
ago. The present distribution of the species therefore results from
re-invasion and migration over huge areas and great distances in a
relatively short time, estimated at 15,000 years since the retreat of the
ice began in earnest. Available paleobotanical evidence suggests that jack
pine survived the Wisconsin glacial maximum at low elevations in the
Appalachian Mountains south of latitude 34° N. and also in the
western Ozark Mountains. From these refugia it migrated to the north and
east and up the Mississippi Valley, and westward around the southern end
of the Lake Agassiz basin (72).

Population Differences

The wide genetic variation found in the species suggests it has large
effective breeding populations, heterozygosity for many alleles, and
strong natural selection against self-fertilization and increased
homozygosity (72).

A study of 33 characteristics of tree crown, bark, wood, foliage, and
cones of mature trees over most of the natural range showed that all
varied significantly according to the geographic origin of the
populations. An average of 37 percent of the variation was due to origin
(74). Environmental factors appear to be the dominant selection
forces responsible for the natural variation over the present-day jack
pine range. The area of optimum development of jack pine is north of the
Great Lakes in Ontario and Quebec (19,47).

Certain traits of jack pine have been demonstrated to be under strong
genetic control including cone shape, cone serotiny, cone volume, cone
length, scale number, number of scales to first ovule, and number of
scales to first seed (53,61,76,79). Early flowering appears to be
under additive genetic control and not under the control of a single major
gene or recessive genes (41). Lammas growth and prolepsis, which may be
detrimental to tree form, are under some genetic control (62,63), and many
of the traits contributing to desirable Christmas tree form are highly
heritable (55).

Races

Numerous jack pine provenance or seed source tests, established
beginning in the early 1940's, have provided information on variation
among provenances (72). Studies of variation have included controlled
environment chamber, greenhouse, nursery, and field experiment.

Growth, the characteristic most frequently emphasized in provenance
studies, has been found to follow a generally clinal pattern associated
with environmental gradients of latitude (photoperiod) and length and
temperature of the growing season at the seed origin (72). Differences in
growth among provenances have been demonstrated beginning at the young
seedling stage and by age 15 to 20 years the differences among provenances
in tree growth and wood production are substantial (72). For example, in a
test of Lake States provenances at 14 locations, trees of two provenances
from northeastern Minnesota were only 71 percent of the plantation mean
height in a central Wisconsin plantation whereas trees of the tallest
source, from Lower Michigan, exceeded the plantation mean by 17 percent
after 20 years (40). Translated to volume growth and considering tree
survival, the volume per hectare of trees in the poorest provenances was
only 38 percent of the plantation mean and that of the best was 187
percent of the plantation mean. These results clearly show the importance
of selecting and using the best provenance or seed source in jack pine
reforestation efforts and the magnitude of the losses in wood production
that may result when seed origin is ignored. Provenance test results in
Canada have similarly shown wide differences in growth among provenances
(72,84,85,86,87).

Most provenance tests show that trees of provenances from areas nearest
the planting sites grow as well as or better than the average of trees of
all provenances (72). In the Lake States, however, trees of provenances
that were moved slightly northward outgrew those of the local provenance
(40). Thus, although wide latitudinal movement of provenances is not
suggested, movement up to 160 km (100 mi) northward in the Lake States can
increase growth. Selection of superior provenances within latitudinal
belts of similar climate should make substantial genetic gains possible
(72).

Biomass production of trees in 24- and 25-year-old plantations of four
Lake States provenances at three locations ranged from 2.7 to 6.1 t/ha
(about 1.2 to 2.7 tons/acre) annually (89). Total biomass and mean annual
biomass were negatively related to latitude of the plantation. Movement of
provenances slightly northward within climatic zones resulted in increased
biomass production of the trees but movement from warmer to colder
short-growing-season zones resulted in poor growth.

Although tree growth has been the single most important trait evaluated
in provenance tests, variation among provenances in other tree
characteristics also has been noted. These include tree form as influenced
by branching characteristics, wood and bark properties, cold hardiness,
autumn foliage color variation in young seedlings, seed yield and quality,
isozyme systems, and numerous instances of genetic variation in
susceptibility or resistance to diseases and insect pests (72).

The vast information available from provenance test results is being
applied to the establishment of seed collection zones, breeding zones, and
regional jack pine improvement programs in the Lake States (44) and in
Canada (72).

Hybrids

Although putative hybrids have been reported between jack pine and
Virginia pine (Pinus virginiana), loblolly pine (P. taeda),
and Japanese black pine (P.thunbergiana) (72), jack
pine x lodgepole pine (P. x murraybanksiana Righter and
Stockwell) is the only verified interspecific hybrid in which jack pine is
a parent (59).

Widely scattered tests of the artificially created hybrids have shown
mixed results, probably because the origin of the parents was not always
matched with the environment of the test site (25,50,58). Tests of the
California-developed F1 hybrids, F2, backcross
progeny, and the two parent species in northern Wisconsin and eastern
Ontario showed that winter injury was associated with affinity to one or
the other parent-it ranged from very severe in the lodgepole pine from
California to none in the jack pine (70,87). Polygenic inheritance was
indicated suggesting that the backcross breeding method might be used to
develop lines suitable for environments tolerated by the hardier parent.

The hybrids and the lodgepole parent were more susceptible to sweetfern
rust and to eastern gall rust than local jack pine in tests in the Lake
States and Ontario (2,84). The form noted in some hybrids suggested some
potential as Christmas trees but not as forest trees (4). However, because
of the high susceptibility to sweetfern rust reported in eastern and
central Canada, the hybrids should not be planted in that region (84).

Natural hybrids between jack pine and lodgepole pine occur in areas of
contact in central and northwestern Alberta (21,61,75) and in scattered
locations in Saskatchewan (5,6). Differences in cone morphology provide
the strongest diagnostic features for distinguishing the hybrids in the
field (61,72).

The turpentine of jack pine consists almost entirely of alpha- and
beta-pinene but that of lodgepole pine is mostly beta-phellandrene with
small amounts of 3-carene and the two pinenes. The hybrid contains
one-fourth beta-phellandrene and three-fourths pinenes. Thus, in the F1
hybrids the bicyclic terpenes of jack pine dominate over the simpler
monocyclic terpene of lodgepole pine in a 3-to-1 ratio (61). Further study
of the segregation for turpentine components in the hybrids suggested that
the composition is probably controlled primarily by a limited number of
genes with major effects (88). Discrimination between lodgepole pine and
putative hybrids with jack pine based on analysis of monoterpenes showed
that the transition zone between the species may be farther west than
previously reported (56).

Duffield, J. W. 1954. The importance of species hybridization and
polyploidy in forest tree improvement. Journal of Forestry 52:645-646.

Eyre, F. H., ed. 1980. Forest cover types of the United States and
Canada. Society of American Foresters, Washington, DC. 148 p.

Ferguson, M. C. 1904. Contributions to the knowledge of the life
history of Pinus with special reference to sporogenesis, the
development of the gametophytes and fertilization. Proceedings of the
Washington Academy of Sciences 6:1-202.

Zavitkovski, J., R. M. Jeffers, H. Nienstaedt, and T. F. Strong.
1981. Biomass production of several jack pine provenances at three Lake
States locations. Canadian Journal of Forest Research 11:441-447.